That article was a little lite on details, does anyone have any idea how groupon will get the details about when you spend money at the merchant? Obviously it's not from the banks, so they must have a deal with merchants. But that deal would require them to modify their point of sale software to support phoning home to groupon. That seems like a tall order for places which have, say, an old filemaker database holding their sales records.

As an aside: Would a merchant really want to turn over all its sales data to groupon?